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Video lesson: Solving polynomial equations on the TI-84

Posted on August 28, 2010

When you are solving a quadratic equation, you have a lot of options. You can factor, complete the square, or use the quadratic formula. But what about polynomials with a degree (highest exponent) that is higher than two? These can be difficult to factor with the types of factoring you learn in a high school algebra class. This video lesson explains how you can use an app included with the TI-84+ Silver Edition to solve a polynomial equation.

There are a couple of catches with using the method described in the video. First, if you have an equation that “skips” a power of x, you still have to include it as a 0 for the TI-84 plus. For example, if you have the equation:

x^3 + 8x -2 = 0

It’s like the “squared term” of x was skipped. That means you would enter the polynomial’s coefficients as 1, 0, 8, and -2.

The other catch is that you won’t get the solutions in radical form. Instead the answers will be returned as decimals. That won’t be enough for a lot of teachers, who will want to see the square root in the answer. Still, if you calculate the answer to the question by hand on a quiz or test, you can still convert that radical answer to a decimal and then use the TI-84 to check that answer instead.

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